1. Field of the Invention
The present invention generally relates to electronic measurement of selected devices under test (DUT)and, more particularly, to measuring selected parameters for various devices using communications link eye diagrams for setting limits to determine whether the DUT performance is satisfactory.
2. Description of the Related Art
When testing communications systems and components as well as other types of systems, it is common practice to set limits for the parameters to be measured. The performance of the DUT results in its parameters being determined by the test. The results found by testing are then compared to the desired limits to determine whether the measured performance is acceptable or not. Devising what limits to use is often part of a specification for standards compliance or the result of knowing the system's desired performance and adding additional manufacturing margin for known variations.
For example, in modern eye diagram mask testing, measurements of the voltage of a multi-valued bit stream versus time are compared to the set region limits to determine whether the voltage sample taken indicates that the voltage of the multi-valued bit was acceptable or not. In this case, if any measured voltages fall outside the defined limit region, then the DUT fails the multi-valued bit stream mask test.
As an additional example, measurements of a single parameter such as the rise time of a multi-valued bit stream signal is compared to a limit such that a visual or audible alarm may be used to signal an “out-of-specification” condition for the rise time of the signal.
Related art in this field includes devices such as digital and sampling oscilloscopes, bit error rate testers and error performance analyzers from companies such as Tektronix, Agilent Technologies, LeCroy Corporation. In at least some of these instruments, measured parameters of the DUT are compared to desired limits to determine whether the measured performance is acceptable. However, none of these instruments or any known instrument analyzes the statistics of the DUT measured performance parameters. Nor does any know device, instrument or system use the performance statistics and the data derived therefrom to extrapolate the expectancy of future performance as measured by the DUT's parameters after test. It is believed that such a collection of statistical information is of vital importance in manufacturing and design of such DUT. Using such information limits can be automatically discovered and used for comparison and/or saved for future use.